玉米联会复合体的电镜观察

以改进的去污剂微铺展技术制备玉米联会复合体标本,硝酸银染色,以光镜和电镜作相继观察。结果表明,三倍体玉米配对时除形成三价体和出现同源转换及双联会复合体外,还出现单价体和非同源配对。本文列出了玉米的SC核型,并对联会复合体侧轴加厚的数目、分布形式作了描述。     

猕猴精母细胞联会复合体的银染色观察

作者以银染的雄性猕猴减数分裂标本,研究联会复合体的形成和行为,特别是性泡内X、Y染色体有规律的变化。指出常染色体联会复合体的形成开始于偶线期,成熟于粗线期,开始消失于弥散期。在粗线期可见20条清晰的常染色体联会复合体,其中1条带有呈深黑色的核仁组织者。X、Y染色体同源区段的配对,开始于早粗线期。随着粗线期的发展,由侧面配对转为端部配对状。性染色体配对的解体也比常染色体联会复合体晚,在弥散期仍清晰可见。在整个前期,X、Y的着色也比常染体联会复合体深。在一些细胞中,X染色体显示一种特殊的“发夹状”结构。这是在性染色体进化过程中X染色体由于易位得到的重复片段在粗线期同源配对的一种细胞学表现。     

四种猕猴属动物精母细胞联会复合体的比较研究

本工作采用去污剂微铺展——硝酸银染色技术研究熊猴、平顶猴、藏酋猴、恒河猴及其亚种毛耳猴的精母细胞联会复合体（SC）核型、SC的结构及其在减数分裂中的行为。结果表明这几种动物的SC核型以及SC的发育过程基本一致。SC的形成开始于偶线期,成熟于粗线期,解体于双线期。在减数分裂前期,性染色体轴呈强嗜银性,配对明显落后于常染色体。根据减数分裂前期性染色体的形态和行为,性染色体的配对可分为五种类型。此外,本文还对XY染色体的同源性和侧轴加粗等现象进行了讨论。     

棕色田鼠性染色体联会复合体配对的形态学研究

以界面铺展———硝酸银染色方法制备棕色田鼠性染色体联会复合体标本,电镜观察了性染色体联会复合体的形成过程。性染色体轴深染加粗,在早粗线期开始联会;中粗线期Ｙ轴以其全长与Ｘ轴约３／８配对,Ｘ轴形成发夹状结构;晚粗线期先于常染色体解联会。并对性染色体间同源性与非同源性配对机制作了探讨     

一位46,XY,t(11;18)平衡易位携带者的联会复合体分析

运用表面铺展联会复合体(synaptonemal cotnplex,SC)的电镜技术对一位46,XY,t(11;18)平衡易位携带者性细胞进行SC观察,分析了30个精母细胞(从早粗线期→晚粗线期)中SC图象,这些精母细胞中均显示了1个性二价体、20个常染色体二价体(SC)和1个四价体。对其中的21个四价体配对行为进行分析,发现有20个四价体发生部分异源配对,其中4、14和2个四价体分别发生在早、中和晚粗线期,发生在早粗线期的异源配对是一种直接的异源配对,与以前报道的发生在晚粗线期经联会调整的异源配对不同。并对该患者发生生殖失败的机制进行了讨论。     

美味猕猴桃原生质体再生植株细胞遗传学研究 Ⅲ .母株减数分裂前期Ⅰ染色体配对的光镜观察

首次报道在光镜下观察美味猕猴桃 (品种 :No.2 6原生质体植株的母株 )花粉母细胞( PMC)染色体在减数分裂前期的配对 ,发现其配对和凝缩有明显不同步性。不同细胞间染色体配对形式变化较大 ,一般以二价联会为主 ,其次由其它多种配对方式 (包括有复合配对、重复配对、着丝点或端粒处联合和多价联会 )形成多价体 ,还有少数未配对或发生内配对 (偶见 )的单价体和几条二价体之间的次级配对。粗线期观察到少数染色体有缺失 (或重复 )、倒位、易位和疏松配对等结构性改变。表明该植株是一个复杂的区段异源六位体 ,少数染色体在结构上累积有变异。还认为该植株是研究减数分裂染色体配对和联会机制的好材料。     

中国人精母细胞和卵母细胞联会复合体的电镜观察

以微铺展技术结合硝酸银染色,对中国人精母细胞和流产胎儿卵巢联会复合体的形态和行为作了电镜观察。列出中国人的SC核型和模式图。根据减数分裂前期XY的复杂形态变化,XY的配对可分为5种类型。对XY短臂之间形成的SC和XY长臂顶端的次级联合以及XY配对的性质和机理作了描述和讨论。本文还报道了一个罕见的三倍体精母细胞,对三倍体精母细胞中SC的配对行为以及和人类染色体疾病病因的可能关系作了分析和讨论。     

卵巢发育阻滞的人工三倍体鱼减数分裂染色体配对的光镜观察

采用界面铺张制片和硝酸银一步染色的方法,对人工三倍体水晶彩鲫卵巢发育阻滞型个体的减数分裂染色体配对进行了光镜观察。在分化有初级卵母细胞的卵巢发育阻滞型的三倍体鱼中,减数分裂粗线期细胞主要的由二价体和单价体组成,也见有少量三价体和其它多价体,其染色体成员数大多在９０左右;在不同细胞间,染色体的大小变化较大;配对联会过程中形成的配对叉和产生的特异蛋白在一些细胞中明显可见。文中讨论了三倍体染色体配对紊乱     

美味猕猴桃原生质体再生植株细胞遗传学研究 Ⅲ.母株减数分裂前期Ⅰ染色体配对的光镜观察

首次报道在光镜下观察美味猕猴桃（品种：Ｎｏ．２６原生质体植株的母株）花粉母细胞（ＰＭＣ）染色体在减数分裂前期的配对,发现其配对和凝缩有明显不同步性。不同细胞间染色体配对形式变化较大,一般以二价联合为主,其次由其它多种配对方式（包括有复合配对,重复配对,着丝点或端粒处联合和多价联会）形成多价体,还有少数未配对或发生内配对（偶见）的单价体和几条二阶体之间的次级配对,粗线期观察到少数染色体有缺失（或重复     

家蚕联会复合体组型分析

作者以表面铺张——硝酸银染色技术制备标本,从亚显微水平对雌、雄家蚕联会复合体(Synptonemal Complex,SC)的行为及组型进行观察和分析。在减数分裂前期,雌、雄家蚕SC的形态和行为均无明显差异。SC的形成起始于偶线期,成熟于粗线期,消失开始于双线期。在粗线期可见28条清晰的SC,在各SC均未见有相当于着丝粒区域的分化结构。无论在精母细胞或卵母细胞中,均未发现异形双价体。从早粗线期到晚粗线期,SC的平均总长由205.5μm伸长至348.9μm。作者根据10个细胞的测量及分析结果,绘制了家蚕SC组型模式图,并就家蚕的性决定进行了讨论。     

Synaptonemal complexes and chromosome chains in the rodent Ellobius talpinus heterozygous for ten Robertsonian translocations

Synaptonemal complexes (SC) in four Ellobius talpinus males heterozygous for ten Robertsonian translocations were examined with an electron microscope using a surface-spreading technique. A total of 136 late zygotene and pachytene spermatocytes were examined. From one to three completely paired SC trivalents were found in each early pachytene spermatocyte. The lateral elements of the short arms of the acrocentric chromosomes in these trivalents were joined with an SC thus forming the third arm of the SC trivalent. At the same stage a few SC trivalents did not contain lateral elements in the pericentromeric region of the metacentric chromosomes and remained unpaired in this region up to mid pachytene. At zygotene and pachytene from two to eight SC trivalents were joined into chains due to formation of SCs between the short arms of acrocentrics of other SC trivalents. These chains are frequent at late zygotene, but are resolved during pachytene into individual trivalents. It is proposed that pairing and SC formation between the short arms of the acrocentric chromosomes results from the monosomy of the short arms and partial DNA homology between these heterochromatic regions. Since crossing over probably does not take place in these segments, the chromosomal chains may subsequently be corrected into trivalents by a dissolution of the SCs combining adjacent trivalents. The correction and disjoining of chains may not be effective in all cells. The cells in which the chains are retained are assumed to be arrested at the pachytene stage.     

The distribution of early recombination nodules on zygotene bivalents from plants.

Early recombination nodules (ENs) are protein complexes approximately 100 nm in diameter that are associated with forming synaptonemal complexes (SCs) during leptotene and zygotene of meiosis. Although their functions are not yet clear, ENs may have roles in synapsis and recombination. Here we report on the frequency and distribution of ENs in zygotene SC spreads from six plant species that include one lower vascular plant, two dicots, and three monocots. For each species, the number of ENs per unit length is higher for SC segments than for (asynapsed) axial elements (AEs). In addition, EN number is strongly correlated with SC segment length. There are statistically significant differences in EN frequencies on SCs between species, but these differences are not related to genome size, number of chromosomes, or phylogenetic class. There is no difference in the frequency of ENs per unit length of SC from early to late zygotene. The distribution of distances between adjacent ENs on SC segments is random for all six species, but ENs are found at synaptic forks more often than expected for a random distribution of ENs on SCs. From these observations, we conclude that in plants: (1) some ENs bind to AEs prior to synapsis, (2) most ENs bind to forming SCs at synaptic forks, and (3) ENs do not bind to already formed SCs.     

In vivo analysis of synaptonemal complex formation during yeast meiosis

During meiotic prophase a synaptonemal complex (SC) forms between each pair of homologous chromosomes and is believed to be involved in regulating recombination. Studies on SCs usually destroy nuclear architecture, making it impossible to examine the relationship of these structures to the rest of the nucleus. In Saccharomyces cerevisiae the meiosis-specific Zip1 protein is found throughout the entire length of each SC. To analyze the formation and structure of SCs in living cells, a functional ZIP1::GFP fusion was constructed and introduced into yeast. The ZIP1::GFP fusion produced fluorescent SCs and rescued the spore lethality phenotype of zip1 mutants. Optical sectioning and fluorescence deconvolution light microscopy revealed that, at zygotene, SC assembly was initiated at foci that appeared uniformly distributed throughout the nuclear volume. At early pachytene, the full-length SCs were more likely to be localized to the nuclear periphery while at later stages the SCs appeared to redistribute throughout the nuclear volume. These results suggest that SCs undergo dramatic rearrangements during meiotic prophase and that pachytene can be divided into two morphologically distinct substages: pachytene A, when SCs are perinuclear, and pachytene B, when SCs are uniformly distributed throughout the nucleus. ZIP1::GFP also facilitated the enrichment of fluorescent SC and the identification of meiosis-specific proteins by MALDI-TOF mass spectroscopy.     

The sequential appearance of components of the synaptonemal complex during meiosis of the female rat.

This paper describes the light microscopy (LM) and electron microscopy (EM) localization of synaptonemal complex (SC) antigens in oocytes of rats. For this purpose, we used monoclonal antibodies (Mabs) that recognize components of 30 + 33, 125, and 190 kDa antigens of SCs of rat spermatocytes. The LM localization was performed by immunofluorescence and the EM localization by immunogold staining. The reaction of the Mabs with oocytes was similar to the reaction with spermatocytes, but weaker. The 30 + 33 kDa as well as the 190 kDa antigens could always be demonstrated if axial elements of the SC were present, irrespective of whether these were paired or unpaired. Thus, these antigens could be detected from leptotene--early zygotene until diplotene. The 190-kDa antigen appeared in a diffuse manner just before the appearance of the 30 + 33 kDa antigens. The 30 + 33 kDa antigens were not only detected in the axial elements of SCs but also in characteristic aggregates, which appeared in zygotene and persisted until after the SCs had disappeared. Such aggregates had rarely been observed in spermatocytes. The 125 kDa antigen was only present in the tripartite segments of SCs, at the inner edge of the lateral elements. Thus, the reaction of the Mab against the 125 kDa antigen was detectable in zygotene, pachytene, and very early diplotene. It appeared later than 30 + 33 kDa and 190 kDa antigens and it disappeared earlier. We found that several steps of the immunostaining procedure could cause variation in the intensity of the Mab reaction.     

Effects of the male contraceptive agent gossypol on meiotic chromosomes of the male rat

Synaptonemal complexes (SCs) of rat spermatocytes were analyzed in silver-stained meiotic preparations 10-24 days after treatment with gossypol acetic acid, 30 mg/kg/day, for 70 days. Gossypol did not affect SC formation or function, as judged by the absence of pairing anomalies, SC fragmentation, or presynaptic arrest. The unpaired lateral axes could be seen at zygotene, and at pachytene normal SCs could be observed. The behavior of the XY axes also appeared to be normal.     

Formation of cytoplasmic synaptonemal-like polycomplexes at leptotene and normal synaptonemal complexes at zygotene in Ascaris suum male meiosis

A thread-like (more than 70 cm long) testis of Ascaris suum, when examined under the light and electron microscope, reveals the linear succession of meiotic stages. Beginning from, at least, late leptotene, the spermatocytes are synchronous in their development. Thus within each transverse section of the testis all the spermatocytes are in the same stage. The spermatocytes at each stage of prophase I occupies several (4 to 10) cm of the whole testis length. — At leptotene, synaptonemal-like polycomplexes of lateral and central stacked elements are formed in the cytoplasm of spermatocytes. At late leptotene, the polycomplexes are attached to the external nuclear membrane. The polycomplexes disappear at zygotene. Slightly discernable axial cores are observed in the late leptotene chromosomes. The synaptonemal complexes (SCs) are formed at the zygotene stage, their structure being characteristically tripartite. The SCs disappear from the nuclei at the diffuse stage of prophase I. In other organisms completely developed polycomplexes of stacked lateral and central elements were never found during the presynaptic period of meiosis, although single or two parallel layers of aggregated central regions of SC were found in Neottiella meiocytes at the stage prior to chromosome pairing (Westergaard and von Wettstein, 1970, 1972). — First appearance of the polycomplexes in the cytoplasm insetead of the nucleus is also a novel fact. It is concluded that the polycomplexes at leptotene are formed by a self-assembly of the SC molecular material precociously synthesized in the cytoplasm. Two hypotheses regarding possible function and the further fate for leptotene polycomplexes are discussed.     

Synaptonemal complex karyotyping in spermatocytes of the Chinese hamster (Cricetulus griseus)

Using the Counce-Meyer spreading technique, in over 70 spermatocytes it was possible consistently to obtain whole, flattened nuclei containing complete sets of pachytene SCs. The SCs are visible in both the phase and electron microscopes. Each SC is morphologically intact, preferentially stained, and attached to the nuclear envelope by a dense, terminal plaque. It is thus possible to trace each SC for its entire length. Also, a structure representing the kinetochore is clearly visible in each autosomal SC. Karyotypes comparable to the somatic karyotype can be constructed by arranging SCs according to length and kinetochore position. The observed regularity of SC morphology implies structural stability sufficient to withstand the stresses imposed by the procedure.— A coarse network of closely packed nuclear annuli connecting SC attachment plaques often provides end-to-end associations and may tend to immobilize SCs during processing.— Three kinds of perturbation of SC structure are encountered. Twists in the SC frequently occur, but no regular pattern or correspondence with chiasma distribution is observed. SCs occasionally hook around each other without disruption, but in two instances the unpaired axis of the X apparently was interlocked within an autosomal SC. Stretching of the SC is infrequent; it is conspicuous when it occurs and is usually associated with other obvious distortions of the nucleus.— Distinctive morphologies of the X and Y chromosomes facilitate their identification in all preparations. — During zygotene, autosomal synapsis, i.e., the formation of SCs from the pairing of single axial elements, initiates at distal ends and terminates at the kinetochore region; neither initiation nor termination is synchronous among all autosomes.     

Synaptonemal complexes of Xenopus laevis.

Synaptonemal complexes (SCs) have been analyzed in spread Xenopus spermatocytes and oocytes. They showed all the usual features of animal SCs in addition to a high incidence of centromere mismatching. A centriole pair is visible throughout zygotene and pachytene. At zygotene the ends of SCs are markedly thickened and are clustered at the nuclear periphery.     

Spreading the synaptonemal complex of Neurospora crassa

A protocol was developed to spread the synaptonemal complex (SC) of the fungus Neurospora crassa. It involves direct mechanical breakage of meiotic cells before spreading. This technique makes it possible to examine the SC of the same nucleus with both light and electron microscopy. This protocol is potentially applicable for other Pyrenomycetes. The SCs were examined at zygotene, pachytene and diplotene. The central elements and the recombination nodules (RN) were well revealed by silver staining. Ten to 13 RNs were counted at pachytene. The total genomic SC length varied with the stage. This whole mount electron microscopy of the SC is particularly useful for studying chromosomal rearrangements.